Epigallocatechin gallate (hereinafter referred to as EGCG) is one kind of catechin extracted from tea leaves, and is attracting attention as a beneficial natural product having an antibacterial effect (Non-Patent Documents 1 to 7). In particular, EGCG has excellent safety because it is naturally derived, and is expected to come into use as an antibacterial agent.
However, for practical realization of such an antibacterial agent, it is desired that the antibacterial effect of EGCG be improved still further.